Power supply system for control unit of internal combustion engine

Abstract

A power supply system for a control unit of an internal combustion engine is provided which is capable of holding an engine controllable state after starting of the engine until the engine is stopped. A relay with a self holding function is inserted in a power supply line exclusively used for supplying electric power from a battery to the internal combustion engine control unit and its related devices. A relay drive and hold circuit 11 receives a relay drive signal and a main switch signal, drives and holds the relay 8 into a power supplying state as long as at least one of the main switch and the relay drive signal from an arithmetic processing section is input to the relay drive and hold circuit.

What is claimed is:  
     
       1. A power supply system for a control unit of an internal combustion engine, comprising: 
       a power supply line exclusively used for supplying electric power from a battery to an internal combustion engine control unit and its related devices;  
       a relay having a self holding function and inserted in said power supply line for switching between supply and interruption of electric power; and  
       said internal combustion engine control unit adapted to receive electric power from said battery through said power supply line;  
       said internal combustion engine control unit comprising:  
       an arithmetic processing section which performs arithmetic processing for various control operations of said internal combustion engine control unit, receives a main switch signal representative of an on/off state of a main switch, which is in an on_state during operation of said internal combustion engine, and a stop switch signal representative of an on/off state of a stop switch, which is made into an on_state when said internal combustion engine is stopped, outputs and holds a relay drive signal when said main switch signal indicates the on state of said main switch, and stops outputting said relay drive signal when said stop switch signal indicates the on_state of said stop switch; and  
       a relay drive and hold circuit which receives said relay drive signal and said main switch signal, drives said relay into a power supplying state and holds this state as long as at least one of said main switch signal indicating the on_state of said main switch and said relay drive signal from said arithmetic processing section is input to said relay drive and hold circuit.  
     
     
       2. The power supply system according to  claim 1 , wherein said battery is arranged at a location apart from said internal combustion engine control unit and said relay, and said power supply line is directly connected from said battery to an internal combustion engine control unit side. 
     
     
       3. The power supply system according to  claim 1 , wherein said power supply system is used for a marine internal combustion engine control unit of a marine vessel, and said battery is arranged in a hull of said marine vessel, and said internal combustion engine control unit and said relay are arranged in said outboard unit, and said power supply line comprises a harness which is directly connected from a hull side to an outboard unit side.